Autism spectrum disorders (ASDs) comprise a wide constellation of neurobehavioral conditions that arise from abnormal patterns of brain development. Several genetic and environmental factors predispose individuals to developing ASDs, each manifesting in certain core behaviors. The long-term goals of our research are to understand the relative contributions of these factors in producing the neural changes that underlie ASDs. The primary objective here is to characterize the alterations to cortical layer 5 projections in the CNTNAP2-/- mouse model of autism. The central hypothesis is that the aberrant migration of neurons to layer 5 in these mice results in enhanced sensorimotor activity from cortical layer 5 to the thalamus and motor centers. Several anatomical and behavioral features of autistic subjects have been identified, which forms the basis for the proposed investigation. The specific aims of the project are to: 1) Determine the neuroanatomical connections of the ectopic neurons that have migrated improperly to layer 5 in the primary sensory cortical areas of CNTNAP2-/- mice and 2) Assess the synaptic properties and functional topography of the layer 5 projections to the thalamus in CNTNAP2-/- mice. This study will utilize a mouse model of the disease to examine the resultant pathological alterations to these forebrain components, which are predicted to account for aspects of the core behaviors associated with ASDs: abnormal social interactions, reduced vocal communication, and repetitive and restrictive behaviors. The proposed experiments are expected to clarify the roles of these and other forebrain components in ASDs and guide our future investigations aimed at directly linking these morphological alterations with autism and ultimately restoring normal behavior in this model system. These experiments will have a positive impact by illuminating the previously unappreciated role of the corticothalamic pathways in ASDs.